Hvi

INTRODUCTION In textile industry, row material is the most dominant factor since it contributes 50-75 % of total manufacturing cost. Any errors or negligence in selection and composition of raw material cannot be corrected by any means. Here omissions are beyond redemption. In case of spg industry the basic R.M. is fibre which has a very high degree of variability. Its measurement is really a tough task but it is often said that If you can measure it then and then only you can manage it. The imp. fibre properties to be measured are length, strength etc. In order to understand the role of imp. properties, we will see the diagram showing that contribution of fibre properties into yarn quality in ring as well as rotor spg (fig.1) Now most of the fibre measuring techniques are labourious and time consuming. In order to avoid this drawback, one instrument developed which gives boon to textile testing and this is known as HVI High volume instrument. These methods are laborious and time consuming. High speed and reliable testing instrument are the present need of mills to produce a good quality yarn. This task is accomplished by HVI instrument.

BASIC BLOCK DIAGRAM OF HVI

Microbalance

SCREEN PRINTER

Colour Length & strength measurement unit

Reflectance

Fineness Measurement Sample Preparation

CONTRIBUTION OF FIBRE PROPERTIES TO YARN QUALITY Elongation

Fineness 15%

5%

Trash 3%

Others 15%

Length 22%

Strength 20% Length uniformity 20%

Fig. Ring Spun Yarn

Elongation

6%

Trash 8%

Others 19%

Fineness 14%

Length 12%

Length uniformity 17%

Strength 24%

Fig. Rotor Yarn

HVI - DATA ANALYSIS • Length

-

Figrogram principle

• Length uniformity

Uniformity index Uniformity ratio

•

U.I. = UHML/ML U.R. = 50% S.L./2.5% S.L.

• Strength -

The force required to break a bundle of fibres clamped by the

combing device. • Elongation -

amount of stretch of fibre bundle prior to break (%)

• Micronoire -

estimation of fineness

• Colour grade -

The Red +b coordinates based on Hunter nickerson cotton

colour chart. • Trash code -

% of trash and area or measured by video principle.

• SFI -

% of trash and area or measured by video principle.

• SFI -

% of short fibres in each sample test specimen.

• SCI -

An index, which indicates the spinnability of a bale cotton.

• CSP -

An index, which indicates the predicted yarn breaking

strength. add matter from file page In Motion Control system (MCI) the fiber length is measured in nonaligned fiber specimen form. This method allows full automatic production of a suitable fiber tuft for measurement. The preparation of specimen includes combing to straighten and parallelise the fibers and brushing to remove fiber crimps. The fiber specimen a theoretically wedge shaped body is lowered in steps of 0.1mm through a slot into a vacuum chamber. The vacuum in the chamber increases as the slot is closed by the wedge shaped fiber tuft The change in vacuum is proportional to the increasing fiber mass in the fiber wedge An extremely sensitive sensor converts the changes in the vacuum into electric signals. The length haracteristics reported by this system are upper half mean length, mean length, uniformity index, short fiber content, etc Uniformity

index is the ratio of the mean length and upper half mean length expressed in percentage. This measure gives an idea about the distribution of fiber length. A value of 80 is considered average length uniformity. The short fiber content gives the percent of fibers smaller than 12.7mm length (by weigh) In Spinlab HVI system the measurement of the length uniformity is made by digital Fibrograph type photoelectric instrument

outputting a voltage directly proportional to the amount of fiber in the prepared specimens at a given distance from the base of the taste beard. The beard is scanned photoelectrically from base to tips the amount of light passing through the beard being upside as a measure of he number of fibers that extend various distances from the comb. The results it reports are 2.5% span length expressed in percentage.

Fineness :In HVI the cotton fiber fineness is expressed as micronnaire value like other air-flow instruments. The principle of measurement is also very much similar to conventional air-flow instruments. The repeatability of the data and the operator ease of performing the tests have been improved slightly by elimination of weighing the samples exactly the samples exactly the specified weight. Some tolerance has been incorporated to reduce weighing time. In a USDA test of HVI system on over 77,000 bales using only one measurement per bale in each laboratory, micronnaire measurements made in different laboratories agreed with each other within O.I micronnair units in 77% of the bales.

A very good

correlation was observed by Balasubramanian, Basu and Ravindranathan between micronnaire instrument.

Fiber strength In HVI the fiber bunch prepared for length testing. Spinlab HVI the test specimen is scanned for length and simultaneously a fibrogrm and the optical mass of the beard are recorded by the microprocessors. Next the comb is positioned for clamping the fiber beard for two jaws spaced at 3.2mm . The rear jaw retracts at a constant rate of extension (C.R.E.) until the fibers are broken. A force reading is taken at 0.02mm of movement and the entire stress -strain curve is recorded. The force is divided by optical mass at amount value of 200 to give the tenacity. Since fibers with smaller diameter scatter more light than the fibers with larger diameter the optical mass is corrected with respective micronnaire value. In MCI models, the length is measured by vacuum and the strength is tested consequently schematic diagram of the principles are shown in Fig 2. Among all other parameters tested by HVI the strength measurements is the most critical as in principle this method is quit different from conventional methods . Various authors

have studied the influence of different parameters on fiber

tenacity value reported by HVI . Though the instrument is calibrated as per

stelometer or pressley strength value there are few basic differences which affect the results. l) fiber strength module of HVI works on CRE principle whereas principle of stelometer is CRT. 2) Rates of bundle extension on the two HVI systems are nearly equal, and both are 10-70 times faster than convential laboratory methods. Stelometer is adjusted to provide a I kg/sec loading rate, where as pressly is set so that the weight travels from 5 Ibs load point to 20 Ibs. load point in one second for HVI, the rate of jaws disablement at 0.13 in/sec for MCI and 0.14 in/sec for spinlab. 3) In stelometer, while preparing samples most of the fiber's take part in bundle strength testing. 4) The mass of fibers are measured indirectly by HVI in place of direct measurement for conventional instruments. The color of cotton fiber is important in gradation of cotton fiber's. For measuring the color, the cotton is placed on glass window measuring 3.5" square. A pneumatic powered automatic pressure plate that applies a constant amount of pressure plate that applies a constant amount of pressure during the test is located above the color window. To measure the color and trash, the operator presses the color start button causing the pressure plate descended to the test window. The calorimeter of HVI uses two lamps to illuminate a sample during

testing reflected light passes through filters and photodiodes to measure the two color component of cotton lightness and yellowness. Lightness is expressed as a percent reflectance(RD%), and yellowness is expressed in terms of Hunter's scale (+b) values. These values can be converted into the equivental USDA color grade codes based on the universal standards for grading American upland and pima cotton. While assessing color, it measures the trash content. The trash meter of this instrument is an automated video image processor that measures the visible leaf or trash. The digital image produces result such as trash area and trash count. Trash area is given by the percent of sample viewing area occupied by trash. Trash count gives an indication of the number of trash particles whose diameter is greater than or equal to 0.01 inch. These two measures, i.e. color and trash are somehow inter-related. It has been observed by lyer that the measures of reflectance(Rd%) has good relationship with trash; the Rd value decreases with increases in trash content. In another publication, lyer have recommended a graded index of Indian cottons based on the colorimeter value of HVI. The trash parameter reported by HVI are quite different as compared to that of shirely trash analyzer. HVI employs optical means to identify trash and below 0.01" , it cannot count whereas Shirley trash analyzer or similar instrument uses gravimetric method where dusts, microdust are also accounted. Very few work has been

carried out in this aspect. Taylor's opined that for counting trash HVI produces low reading for tinged and yellow stained cotton compared to the trend indicated by other cotton's, the difficulty in counting trash in yellow cotton can be explained two factor's. Firstly, in this type of cotton much of the visible trash is composed of motes immature seeds and short fiber. Which are hidden from the view of the camera and, secondly, the reduces contrast between brown trash and yellow cotton makes it difficult to identify the edge of a particle.

Applications :How is HVI used ? Cotton Seed Breeders

:

Verify progress in attaining goals in development of new varieties of cotton.

Cotton Producers and

:

Government standards Cotton Merchants/Shippers

value and spot market price of cotton. :

Cotton Consumers/Spinners Cotton research

Grading/Classification for use in loan

Verify published data on cotton classification.

:

Basic research and investigation of various physical properties of fibre.

Modern Quality Concepts based on HVI

Bale

Yarn

Management

Engineering

System (1) Bale Mgt :- It is based on categorising the cotton bales according to fibre quality characterstics. It has 3 steps. (1) Measurement of fibre properties of each bale. (2) Separation of bales into class (3) Making a balanced min. Ist step is entirely based on HVI testing. (2) Yarn Engineering :- It is nothing but prediction of yarn properties from fibre properties and Quick fibre analysis can be possible on this instrument.

HIGH VOLUME INSTRUMENT TESTING - THE BASICS  Properties Measured

-

length, strength, length uniformity elongation, micronaire, colour and trash.

 Equipment features

-

VGA colour monitor IBM - Compatible computer 3.5 " floppy drive Hard disk drive, balance, printer

 HVI 900 system Modules :900 Semiautomatic

900 Automatic

Length/strength module micronaire module colour / trash module

COMPARISON OF HVI AND LABORATORY INSTRUMENT Property 1) Micronaire 2) 1/8 gauge strength 3) 1/8 gauge elongat'n (%) 4) 2.5% S.L. span length 5) Uniformity Ratio

Lab 4.2 21.3 6.6 37.1 51.1

HVI 4.2 21.0 7.1 36.9 51.2

Lab 5.2 24.2 8.1 31.4 47.7

HVI 5.2 25.2 7.8 31.8 47.5

Lab HVI 3.2 3.2 21.5 22.5 6.0 6.3 28.6 28.8 45.9 46.0

PREMIER HFT 9000 V 2.1.1 HFT System Testing

Date: 08/12/2002

Identifier : LOTN044

Time : 11:41

Cotton : MECH1

Operator : JKU

Sub 2.5% 50% ID SL SL 44/23 28.2 13.5 8 2 44/11 27.5 12.9 7 1 44/12 28.9 13.9 6 2 44/42 67.8 13.11 3

U.R. MIC

Str

Elg

Rd

+b

C.G

MR

47.8

3.96

24.4 6.5

SFI (w) 69.6 10.1 43.1 0.84 9.9

46.8

3.99

23.9 6.5

67.9 9.7

48.1

3.97

22.6 6.5

67.7 10.3 43.1 0.83 8.9

47.1

3.86

22.3 6.4

70.5 10.1 42.1 0.83 10.9

42.4 0.84 11.4

Advantages of HVI 1. High accuracy, which will causes to give more precise result and are can predict almost clearly at each stage.

2. High speed can test almost 200 samples/hr. due to that results are based on large no. of results and completely free from biosing. 3. Result are free from human and machine error. 4. Gives additive quality indices namely S.F.I., S.C.I., C.S.P. 5. Avoider labour's laboratory work.

Conclusion :In Today's worldwide competitive market, effective management of cotton is only possible by HVI. It is said to be heart of fibre measurement technique.

Bibliography :(1) Principles of textile testing

-

J.E.Borth

(2) Cotton fibre testing

-

Ed White, Peter Jones.

(3) A. T. I. March 1998 (4) Textile Research Journal - April 1992 (5) I T J = June 1995 (6) A T J Feb 1999.

TESTING METHODOLOGY IN THE PAST Parameter Length

Instrument Classer grade

Measure Staple length

Grease plate

Mean length, eff. length

Bare sorter

Mean length, dispersion etc.

Digital fibregraph

2.5%, 50% span length uniformity ratio etc.

Strength

Fineness

Maturity

Trash

Stelometer

Bundle strength

Pressley

Bundle strength

Instron

single fibre strength

Gravimetric method

Fineness

Optical

Fineness

vibroscope

Fineness

air flow

Fineness

Differential dyeg method

Maturity

NaOH method

Maturity

Polarized Method

Maturity

Shirely trash analyser

Trash %